There have been a number of tragic cases where tall buildings have caught fire for various reasons, and fire-fighters on the ground appear to have been unable to reach the upper stories with fire hoses.

As a child watching 9/11 unfold, I remember wondering why, given that helicopters were being used to film the events, it would not be possible for helicopters, or perhaps airships, to be loaded with water or foam and fly over burning buildings, dousing them.

Of course, in retrospect, I understand that the World Trade Centre buildings were so vast and the fire (and structural damage) so enormous that this would have made little practical difference. But what about cases of relatively smaller tower blocks, such as the recent tragedy in the Grenfell block in London?

I assume that there must be some practical reason why this cannot be done, on the grounds that this is something which presumably would be being done if it were possible.

Is it simply that the weight of a large amount of water would be too heavy for a helicopter to carry? Would this apply to airships?

$\begingroup$Mostly because the fire is inside the building, and dumping water on the outside of the building and roof wouldn't stop the burning on the inside.$\endgroup$
– Ron BeyerJul 2 '17 at 15:50

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$\begingroup$One thing is heat from fire will create strong turbulent column of rising air. Helicopter or any aircraft does not like anything turbulent. To drop anything on precise location needs specific positioning which is not easy to do here. Weight is not a problem as you sometime see helicopter drop water to fight forest fire.$\endgroup$
– vasin1987Jul 2 '17 at 15:51

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$\begingroup$@RonBeyer In the case of the Grenfell tower, the problem seems to be that the fire was NOT just inside the building, but travelled up the exterior cladding. This meant that the usual fire precautions designed to prevent fires spreading between flats failed. Dumping water on the exterior cladding might have helped in this case.$\endgroup$
– DrMcCleodJul 3 '17 at 9:39

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$\begingroup$One (well, this one) wonders if something akin to the infamous "puff the magic dragon" could make repeated slow flybys of a burning building, with its internals stuffed with foam and hoses rather than guns n' ammo. They are already proven at flying above and around areas from which "materials possibly injurious to the wellbeing of craft and crew" may be emitted.$\endgroup$
– Grimm The OpinerJul 4 '17 at 10:09

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$\begingroup$@GrimmTheOpiner agreed, about six AC-130 water bombers with fire nozzle where the howitzer goes, and ability to scoop water while flying, could've saved WTC. But while we're at it, an H-4 Hercules with an integral wet-dock containing a DSRV could've saved the Kursk crew. The difficulty is in the probability and practicality of having such an exotic single-purpose bird exist, and be in exactly the right place at exactly the right time. Maybe if they had FTL...$\endgroup$
– Harper - Reinstate MonicaJul 5 '17 at 4:01

The Ka-32A11BC proved its fire-fighting credentials in April 2012, when a blaze engulfed ... the 67th floor at the Federation Tower in Moscow, Russia, more than 270 meters above ground level. ... the fire was only contained after two Ka-32As belonging to the Russian Emergencies Ministry were called into action and ferried in water from the nearby Moscow River.

However, there are multiple issues in using helicopters for urban firefighting.

Helicopters are all but powerless is case of fires breaking out over the lower floors. Even in the above case, the helicopters were useful only as the fire broke out in the top floor of the (then under construction) skyscraper. For lower floors, the helicopter would have to carry the spraying equipment in the fuselage, which would make the useful payload impractical. Airships are all but useless in this case, while even helicopters would have difficulty getting through the buildings.

Firefighting using helicopters is not a precision business as it would be difficult to position the helicopters directly overhead due to the intense heat and the turbulence produced. For safety, the helicopters have to fly higher, which reduces efficiency due to winds.

It costs up to \$14,000 a day to keep an air tanker on call and as much as \$4,200 per hour to put it in the air. Heavy-duty helicopters, the workhorses of aerial firefighting, can cost \$32,000 a day on standby, plus \$6,300 per hour of flight time.

and this in the US where the need to put out forest fires is all but certain. Major fires in skyscrapers are infrequent and too scattered around the world to justify the expense of keeping a helicopter on standby in any given city.

But unpredictable atmospheric conditions make flying over wildfires difficult and dangerous. Thirty-seven firefighters have died in aerial firefighting accidents in the last decade.

Urban environment with high rise buildings and power lines pose a separate set of challenges.

Water and firefighting slurry supplies have to made available- this is important in cases where for example, the rivers are seasonal. Not only is the normally used firefighting slurry costly, it is also not environment friendly.

... the slurry, which is rich in nitrogen, can harm fish, wildlife and watersheds, despite agency guidelines to prevent drops onto vulnerable areas.

Aerial firefighting is expensive. Tankers cost upwards of \$6,000 per hour to operate. The slurry itself averages about \$2 per gallon, and the Forest Service used almost 9 million gallons of it last year.

Airships have the same issues, and some more (payload and speed/maneuverability come into mind).

$\begingroup$Just out of curiousity, why are standby costs so high? The figures quoted equal 3-5 hours of actual flight time just to stand by for the day. Are they sitting on the tarmac idling and burning fuel for that period? Does it cost a lot to pay people to just sit there? Or is this just what they charge because they could have averaged that much time in the air had they not been on standby?$\endgroup$
– MichaelJul 3 '17 at 0:19

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$\begingroup$@Michael Note that the article quotes the cost to keep the aircraft 'on call'- practically ready to fly. In that case, the aircraft and crew must be flight worthy and ready; while the aircraft may or may not be fueled, it will be in a short notice- you're going to pay for the fuel service. It is basically like keeping the taxi waiting the whole day- you're keeping the aircraft that could've been used somewhere else by paying for it. Add to this the expenses for parking and ground support/handling equipment, you get the figure.$\endgroup$
– aeroaliasJul 3 '17 at 1:11

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$\begingroup$Also note that winds between tall high rises can be pretty extreme, fire or no fire. That's the main reason why airships don't currently dock with the Empire State Building as originally intended by its designers.$\endgroup$
– posfan12Jul 3 '17 at 4:02

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$\begingroup$Couldn't we just build a very long fire hose, attach it to the helicopter, and then use the helicopter to point the hose at the fire? That would eliminate the need for the helicopter itself to carry the water internally?$\endgroup$
– mickburkejnrJul 3 '17 at 10:40

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$\begingroup$@mickburkejnr: The weight of the water in the hose will exceed the capability of the pump before you get high enough to be useful.$\endgroup$
– John BodeJul 3 '17 at 18:06

Fire creates heat, which in turn creates turbulence. While soaring enthusiasts welcome this as thermals, lighter-than-air captains dread such turbulence as their worst enemy. When the airship enters such a warm updraft, first the nose is lifted, and then the whole ship. At the same time, the airship starts to drop within that hot, rising air column, because now the density of the outside air is reduced, reducing buoyancy. The ship will be tossed around and be very hard to control.

Dropping a large load at the same time makes matters worse. Now the ship has excessive lift and will accelerate upwards like a cork in water. If that upward movement cannot be stopped before the bounce height of the ship is reached, the gas bags will burst.

No, airships are completely unusable to fight fires.

Helicopters, on the other hand, make excellent precision firefighters. They can carry a limited load but place this with much higher precision than airplanes. Airplanes have an advantage in cost per ton of water and when the source of that water is some distance away.

In all cases, water would only be dropped from above, like rain, and buildings are designed to prevent rain from entering. Therefore, unless the roof structure is ablaze, this water would not reach the burning structure. With current technology, fires on higher floors of tall buildings can only be extinguished with a pre-installed sprinkler system or firefighters using water from pre-installed standpipes and hoses. Optimistic scenarios of helicopters shooting jets of water horizontally into a burning high-rise building have not materialized because the reaction force from shooting that jet of water would make the helicopter hard to control.

$\begingroup$But note that helicopters can only drop water on the top of things. If a high-rise building is on fire, you almost certainly want to throw water at the side of it, which conventional firefighting helicopters can't do.$\endgroup$
– David RicherbyJul 3 '17 at 9:47

$\begingroup$@DavidRicherby: In that, they are not much different to airplanes. They are not ideal for urban firefighting, but still better than airplanes.$\endgroup$
– Peter KämpfJul 3 '17 at 17:11

$\begingroup$Optimistic scenarios of helicopters shooting jets of water horizontally into a burning high-rise building have not materialized because the reaction force from shooting that jet of water would make the helicopter hard to control. AH64 pilots are pretty darned skilled with an anti-tank cannon though.$\endgroup$
– KoyovisJul 4 '17 at 15:58

The most extensive use of helicopters for firefighting (and sealing a reactor) was Chernobyl. The Helicopters of Chernobyl In fact, nothing but a helicopter could possibly have performed the partial sealing of the exposed reactor, preventing a far worse release of radiation.

Sadly, the crews of those helicopters who responded immediately, died from radiation exposure not long after the initial disaster. The very radioactive helicopters were quarantined in a field for decades, until they were eventually destroyed to stop looting of parts.

Large airships... are just too vulnerable to extreme weather to be considered a reliable tool. While everyone remembers the fire of the Hindenburg, the only non wartime loss of an airship to a hydrogen fire, few remember the large dirigibles lost to storms: three notable examples are the USS Akron, USS Macon, and the British R101.

Helicopter firefighters do exist, and are used here in Australia for extinguishing bushfires. Elvis is here on a regular basis.

Bushfires just require to plonk a load of water on top of the burning area (just, as in doing a heroic job flying above a roaring fire) - spraying a water jet sideways from a heli would be more complicated but could probably be done, the dynamics would be analogous to those of a cannon on an attack helicopter. Airships might work yeah, the helium filled ones, if only they wouldn't blow away.

It probably boils down to a question of economics. This document lists the number of fires in tall buildings, and mentions that built-in fire suppression systems are effective. The Twin Towers was a highly visible event, but how many tall building fires are there per year in NY City, and would that justify having a highly specialised team of helicopters availabe, with the pumping equipment and amount of water on board to squirt sideways into mid building?

Helicopters don't have much speed and range and each big city with skyscrapers would have to maintain a fleet. There are 12 fires in tall buildings listed for New York City in the last 100 years in Wikipedia. It would be conceivable to seek cooperation with the Army to use attack helicopters and exchange cannon & ammunition for a water cannon & water payload - the highly trained expert pilots would do a grand job at this.

$\begingroup$Whoa - according to this site, during the seventeen year period ending in 2002, 1600 civilians died and over 20,000 were injured in the approximate 385,000 high-rise building fires in the United States, excluding the MGM Grand Hotel and the Las Vegas Hilton fires in the early 80’s, and the World Trade Center on September 11, 2001.$\endgroup$
– Peter KämpfJul 3 '17 at 20:43

$\begingroup$Here are some statistics about high-rise fires in the USA. The linked PDF has even more statistics, including: the majority of high-rise fires start on the sixth floor or below; fires in high-rise buildings are less likely to spread than fires in shorter buildings (due to having more suppression systems); and seven out of ten of the deadliest high-rise fires in history started on the third floor or below. ...$\endgroup$
– Michael SeifertJul 3 '17 at 21:28

$\begingroup$In other words, very few high-rise fires are sufficiently high and sufficiently large that the ability to douse the fire from outside the building would be useful. It's just that those that do spread to this point are the highly visible ones: World Trade Center, Grenfell Tower, Address Hotel, One Meridian Plaza, etc.$\endgroup$
– Michael SeifertJul 3 '17 at 21:43

Special airplanes and specially equipped helicopters ARE used to fight fires, mainly forest fires.

In parts of Europe, where I live, the name "Canadair" was synonym with the special firefighting planes, such as Canadair CL-215 and Canadair CL-415. Through my youth I was convinced that Canadair manufactures only firefighting planes, and only later I found out that they make passenger planes as well.

So the answer to that part is, they are used.

As to why they are (mostly) not used in urban environments, the answer is, there are better ways to prevent and fight fires in urban environments, so the need for a firefighting aircraft in urban areas is very infrequent. In properly maintained urban buildings you have fire alarms, sprinklers, and good access for the fire engines - while in the remote forests you have no such things.

Forest fires in southern Europe are quite regular and predictable occasion (due to tourists/visitors, sparks from the railways, etc.) so you can be sure that the fleet of firefighting aircraft in any country will be engaged for large part of the summer (and when not in use, they will be sent to help to their neighboring countries to help).

As people already explained, maintenance of these aircraft is costly and you cannot expect them to be sitting ready on the tarmac in London (for example) for 10 years without any engagement, until a fire breaks out in the building that was refurbished with flammable materials in what it seems now a criminal negligence. They also need time to be loaded with water (and perhaps chemicals, depending on the nature of the fire). When fighting fires in the wild (forests) they are never used alone (or even as first response), but always in combination with firefighters on the ground, if the terrain is difficult to access.

So, sadly, while a fully loaded Canadair CL-415 sitting on the tarmac with pilots ready for action 24/7 would perhaps help in Grenfell tower fire, having such aircraft ready 24/7 in urban environments simply does not pay off. And if it would not have been ready 24/7 it could not make any difference, since with Grenfell, the building was engulfed with flames within half an hour, if I remember correctly.

Of course, the issue of flying low in the city during the night over the fire also poses far greater risk than flying over a remote burning forest with accurately mapped topography (elevation).

First, the fire is inside the building, and dumping water on the outside of the building and roof wouldn't help.
Second, the upper part of the building being burned is very likely to fall down. The pulling of fire-fighting material may make it worse.

$\begingroup$Agreed, in the case of Twin Towers the fire was not on the top floors and would have required sideways squirting of the extinguishing material. However, in case of Grenfell tower in Britain, just dumping water would have helped.$\endgroup$
– KoyovisJul 3 '17 at 11:38

$\begingroup$@Koyovis The fire at Grenfell Tower began on (iirc) the fourth floor and spread upwards. I don't see how dumping water from the top would have helped any more than it would have on the Twin Towers.$\endgroup$
– David RicherbyJul 3 '17 at 11:52

$\begingroup$Was it established that the cause of the Grenfeel Tower fire was the external cladding?$\endgroup$
– KoyovisJul 3 '17 at 12:14

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$\begingroup$@Koyovis no, the cause was a faulty kitchen appliance. The spreading of the fire may or may not have been (in part or entirely) due to the external cladding.$\endgroup$
– Jamiec♦Jul 3 '17 at 15:23

$\begingroup$Oh right-o. I don't claim to be a fire-fighting expert.$\endgroup$
– KoyovisJul 3 '17 at 15:28